The present invention relates to a device for the transverse retention of a longitudinal test specimen, notably having a stylized L-shaped or S-shaped cross section, and to an apparatus for the mechanical characterization of such a test specimen in bending.
The invention is particularly well suited, although not exclusively, to the three-point or four-point symmetric or asymmetric flexural characterization.
In the known way, three-point or four-point bending tests are used in order to study and characterize the resistance to loading of new materials (for example metallic materials, composite materials, etc.).
The principle behind these bending tests is to subject a test specimen made of a material that is to be tested, of given dimensions, to a deformation that is defined by a constant strain rate and to measure the force with which the said test specimen opposes this deformation. In this way it is possible to determine the mechanical behavior, the physical properties and the characteristics of the material of which the test specimen is made.
There are two families of bending test:                simple bending tests (also known as three-point tests) which are defined by a single central pressure point at which the bending force is applied and two reaction points on which the respective ends of the test specimen rest; and        four-point bending tests which are characterized by two central pressure points via which the bending force is applied and two reaction points supporting the ends of the test specimen.        
Furthermore, the reaction points supporting the test specimen can be of two types, namely:                either linear, in which case contact between the supports and the test specimen is tangential;        or surface, in which case contact between the supports and the test specimen is defined by a contact face.        
Whatever the type of contact, the main operating parameters for these test are the bending force applied to the test specimen and the distance separating the two opposite contact points of the reaction points supporting the test specimen.
Document FR2937731 already discloses an apparatus for the flexural characterization of a longitudinal test specimen having a lower face and an upper face that are substantially parallel. In particular, the apparatus comprises bearing means that have the ability to rotate about an axis with respect to a fixed support and attachment and adjustment means for adjusting the positioning of the test specimen relative to the bearing means. When the test specimen is deformed under the effect of the central force, the bearing means undergo a rotational movement about the axis of rotation so that the points of contact between the test specimen and the bearing means remain aligned with said axis of rotation.
However, the abovementioned apparatus proves to be ill suited to the flexural characterization of test specimens of a stylized S-shaped cross section defined by two lateral flanges joined together by an orthogonal web. This is because applying a bending force to such a test specimen retained by the bearing means of such an apparatus generally causes the web to tilt as a result of a moment generated by opposing forces applied to the lateral flanges.
It is an object of the present invention to overcome this disadvantage.